Fig. 6

Altered Pax protein distribution correlates with abnormal segregation of the optic primordia into optic stalks and retinae in embryos injected with shh RNA. Rostral is to the left in A-C and F. All embryos in this figure showed only moderate reduction in the extent of the retinal tissue. Embryos are labelled with anti-Pax2 (A-F), HNK1 (G) or anti-Pax6 (H) antibodies. (A) Lateral views of 24 hour injected (left) and wild-type (right) embryos. The arrowheads indicate sites of Pax2 expression at the midbrain/hindbrain boundary, in the otocysts, in hindbrain neurons and in the nephric duct. (B,C) Ventral views of wild-type (B) and injected (C) embryos. (D,E) Frontal views of wild-type (D) and injected (E) embryos. The arrows in E indicate the expansion of Pax2 expression in the optic stalk region of the injected embryo. (F) Horizontal section through the retina of an shh-injected embryo at 2 days of development. The distal extent of Pax2 distribution (arrowheads) is coincident with the proximal limit of pigment epithelium formation. Most of the cells in the deeper layers of the retina still contained Pax6 at this stage as judged by anti-Pax6 labelling of adjacent serial sections. (G,H) Frontal sections through the retina of an shhinjected 5-day old fish labelled with HNK1 antibody (G; brown labelling of axons) or anti-Pax6 antibody (H). At this stage Pax6 protein is restricted mainly to amacrine cells (Macdonald and Wilson, unpublished observations). The antibody labelling reveals relatively normal lamination of the neural retina. The arrows indicate medial regions of the neural retina over which there is no pigment epithelium. Abbreviations: a, amacrine cell layer; g, ganglion cell layer; hy, hypothalamus; inl, inner nuclear layer; ipl, inner plexiform layer; l, lens; nr, neural retina; os, optic stalk; p, photoreceptor layer; pe, pigment epithelium; t, telencephalon. Scale bars, 50 μm.